Circuit breaker



Sept. 27, 1949. H. M. WILSON 2,482,955

CIRCUIT BREAKER Original Filed April 22, 1943 Patented Sept. 27, 1949 CIRCUIT BREAKER Harold M. Wilson, Lexington, Mass., assignor'to Metals & Controls Corporation, Attleboro, Mass, a corporation of Massachusetts Original application April 22,

Divided and this application Decemher 8, 1947, Serial No.

This invention relates to combined electromagnetic and thermal protective circuit breaker systems, and more particularly to remote-control circuit breaker systems of for use on aircraft and the like.

This application is a division of my co-pending application of the same title, Serial No. 483,984,

filed April 22, 1943, now Patent No. 2,434,186.

Among the several objects of the invention may be noted the provision of a simple form of manual reset, combination magnetic and thermal circuit breaker system for openin a load circuit if currents of dangerous value flow therein; the provision of apparatus of the class described arranged to permit placement of a control switch on an operating panel without the use of large copper conductors to outlying devices; the provision of apparatus of this class which permits the use of a remote-controlled circuit breaker as large as needed near an outlying device, and the provision of a circuit breaker of this class wherein the thermal responsive element is not called upon to carry all of the load current. Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application oi. which will be indicated in the following claims.

In the accompanying drawing, in which one of various possible embodiments of the invention is illustrated, the single figure is a vertical section of the circuit breaker and a wiring diagram of the system of this invention.

Referring to the drawing, there is shown at numeral I an electrical load, such as an electric motor or similar translatingdevice, which is connected in a load circuit energized by a suitable source of power, herein illustrated as a battery 3. The load circuit is controlled by the combined electromagnetic and thermal circuit breaker C of this invention. The circuit breaker comprises a solenoid switch S having a solenoid coil fixed in a case 7 surrounding a guide 9. Sliding in the guide is a magnetic armature core H which has an extension |3 of reduced diameter extending out of the guide. A bus bar switch. arm 5 is riveted on the outer end of extension i3 as indicated at l1. The switch arm carries contacts l9 facing the case 1. These contacts are cooperable with contacts 2| fixed on but insulated from case 1.

this class particularly 1943, Serial No.

8 Claims. (Cl- 175-294) The armaturecore II (and its extension 3) 55 and switch arm l5 are biased outward by a spring 23 reacting from a flanged portion 25 01' the guide 9 against the arm. The flanged portion 25 also acts as a. stop limiting outward movement of the arm. The latter is movable toward the case 1 against the bias of spring 23 when the solenoid coil is energized to close the solenoid switch by engaging the contacts l9 and 2|. Current may thereupon flow from one of fixed contacts 2|' through the arm l5 to the other contact 2|.

The circuit breaker includes a thermal switch T adapted under non-overload conditions for connection in shunt with the arm I 5 to carry a part of the load current. This thermal switch controls a holding circuit for solenoid coil 5, as will be made clear. It comprises an electrically conductive thermostatic element 21, herein illustrated as a snap-acting thermostatic disc of the type known in the art as a Spencer disc, having contacts 29 thereon. mounted by a screw 3| on the outer end of a pin 33 of insulating material threaded into the outer end of armature extension i3. The disc 21 is mounted to snap upon overheating from a normal position wherein its contacts 29 engage a set of contacts 35 on the arm l5 and close the holding circuit .to a. position wherein contacts 29 and 35 are disengaged to open the holding circuit. A pin 31 of insulating material extends from the solenoid body through apertures 39 and ii in the arm I 5 and disc 21, respectively, for maintaining the contacts is and 2| of the solenoid switch and the contacts 29 and 35 of the thermal switch in alignment.

The load is connected in series with the battery 3 and the solenoid switch S in a load circuit designated 43. This load circuit is completed when switch S is closed, 1. e., when the bus bar switch arm i5 is in a position wherein contacts l9 and 2| are engaged. Under such conditions load current flows through the arm. If the disc 21 is in its normal position closing contacts 29 and 35, part of the load current will flow therethrough.

A holding circuit for the solenoid switch is connected across the battery and includes the switch S and the thermal switch T in series. As illustrated, the disc 21 is connected through a pigtail connection and a line 41 to one terminal oithe coil 5. The other terminal of the coil is connected by a line 49 to the load circuit 43 at a point on the other Side of the battery with respect to the switches.

The above-described arrangement is such that The disc is centrally.

when the arm I5 is moved inward with respect to the solenoid to close contacts is and 2|, load circuit 43 is completed to energize the load Assuming that the disc 21 is not overheated and is in its normal position closing contacts 25 and 35, the holding circuit for the solenoid coil 5 is completed from one terminal of the battery 3, through the arm |5 of switch S through disc 21, pigtail 5, line 41, coil 5, and line I! to the other terminal of the battery. Coil 5 is thus energized to hold the arm i5 circuit-closing position.

The disc 21 is calibrated to heat and snap to open-circuit position at predetermined overload shunt current therethrough. Thus, upon overload, the disc 21 snaps to disengage contacts 29 and 35, thereby breaking the holding circuit. Spring 23 thereupon biases arm I5 outward to disengage contacts I! and 2| and break the load circuit.

One way of initially energizing the holding circuit through coil 5 to make the load circuit is manually to move the arm ii to circuit-closing position. It is preferred, however, to provide a remote-control reset switch 5| for energizing solenoid coil 5 to close the solenoid switch S and establish the holding circuit. The switch 5| has contacts 53 movable against the bias of spring 55 to close contacts 51. One of-contacts 51 is connected by a wire 59 to load circuit 43 on one side of the battery 3. The other contact 51 is connected'by a wire 5| to line 1 on the other side of the battery. Thus, when switch 5| is closed, a circuit is completed from the load circuit on one side of the battery through line 59, switch 5|, line 5|, part of line 41, coil 5, and line 49 to the load circuit on the other side of the battery. This energizes coil 5 to close both the load circuit and the holding circuit for coil 5 (assuming disc 21 to be in its normal position closing contacts 29 and 35), and switch 5| may be released without opening the load and holding circuits.

Wires 58 and 6| may be small since they carry only a small amount of current. Thus, switch 5| may be located on a control board remote from the circuit breaker C without use of heavy control wires. This is desirable, particularly in aircraft installations, where saving in weight is essential. At the same time, use of switch 5| permits disc 21 to be located close to the load i if it is desired to protect the load from overheating. For example, in such instances the circuit breaker C may be strapped directly to a motor or generator and the wires 59 and 5| carried over to switch 5| on the pilots instrument panel. It is to be understood, however, that the circuit breaker need not be near the load where the object is simply protection against overload currents.

It will be understood that the thermostatic element 21, while preferably a snap-acting disc of the Spencer type, may be of a strip, creepacting or other type under circumstances of low current value in the work circuit.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

in loaddisengageable with said fixed contacts I claim:

1. A thermostatic switch comprising fixed contacts, a fixed solenoid coil, an assembly comprising a movable contact bus engageable and and organized with a movable armature responding to energization of the coil, means biasing said assembly toward disengagement of said bus irom said fixed contacts, a thermostatic member mounted on and bodily carried with said bus, movable contacts controlled by said thermostatic member and adapted when said member is cold electrically to engage the bus to form a shunt path through said thermostatic member, said thermostatic member when hot moving to a position to break the shunt circuit therethrough, a load circuit including said fixed contacts. a holding circuit including said thermostatic member when it is in cold position and also said bus, and manually-operable means for initially moving the assembly of said armature and bus to engage the bus with said fixed contacts.

2. A manually resettable circuit breaker comprising an electromagnetic switch having a coil and a switch arm controlled thereby for making and breaking a load circuit, a thermal switch comprising a thermostatic element normally connected in shunt with said switch arm and disconnectable therefrom upon overheating, said thermal switch being connected in series with the coil and the switch arm of the electromagnetic switch in a holding circuit for the latter so that the coil is energized when both the electroma netic and thermal switches are closed.

3. A manually resettable circuit breaker comprising an electromagnetic switch having a coil and a switch arm controlled thereby for making and breaking a. load circuit, athermal switch comprising a thermostatic element mounted on the switch arm for movement, upon heating, from a normal position wherein it is connected in shunt with the switch arm to a position wherein it is disconnected from the switch arm, said thermal switch being connected in series with the coil and the switch arm of the electromagnetic switch in a holding circuit for the latter so that the coil is energized when both the electromagnetic and thermal switches are closed.

4. A manually resettable circuit breaker comprising a solenoid switch having a coil and a bus bar switch arm controlled thereby to make a load circuit upon energization of the coil, a thermostatic element mounted on the switch arm for movement, upon heating, from a normal position wherein it engages the switch arm to provide a shunt path through said element to a position disconnected from the switch arm, and a holding circuit having said thermostatic element, switch arm and coil connected in series.

5. A circuit breaker as set forth in claim 4, further including a solenoid-energizing circuit including the solenoid coil and a reset switch.

6. A manually resettable circuit breaker systern comprising a load, a load circuit including a source of power and a solenoid switch having a coil, an armature movable in response to energization of the coil, and a switch arm mounted on the armature for making the load circuit upon energization of the coil, the switch arm being biased to load-circuit-breaking position, a snapacting thermostatic disc mounted on the switch arm for movement, upon heating, from a normal position wherein it engages the switch arm and provides a shunt path through the disc to a position disconnected from the switch arm, and a coil, and a switch arm mounted on the armature for making a circuit when the coil is energized, the switch arm being biased to circuit-breaking position, a snap-acting thermostatic disc mounted on the switch arm for movement with the switch arm and for movement relative to the switch arm between a normal cold position wherein it engages the switch arm and provides a shunt 8 a path through the disc and a hot position wherein it is electrically disconnected from the switch arm, said disc being connected in series through the switch arm with the coil in a holding circuit for the latter so that the coil is energized when the switch arm is in circuit-making position and the disc is in normal cold position.

- HAROLD M. WILSON.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PA'rmrrs Number Name Date 1,764,374 White June 17. 1930 1,922,452 Parks et al Aug. 15, 1933 1,932,808 Van Valkenburg Oct. 31, 1944 

